300 Rum finish reamer

Active Member

I may need to borrow/rent a 300 Remington Ultra Mag finish reamer to touch up my chamber. It is a factory Remington 700 but seems to be on tight side. A warm chamber is hard to close on a factory loaded cartridge. Does anyone know where to borrow or rent one? I am also trying to find someone with a RCBS Full Length resizing die to see if they work better than the brand of dies I currently have. I would like to resize a couple of my brass and see if the RCBS dies will do a better job for my gun. I have a press set up for portability and could meet you. I am in Vancouver WA. Bill

Active Member

This doesn't add up. If it's a factory rifle then the place to start is with a go-gauge. I wouldn't ream it for some possibly out of spec factory ammo. Is this a custom rifle? If so it sounds like it was headspaced on a brass rather than a go gauge. Brings us back to the go gauge. Are you using a full length sizing die now? If you are using a neck die like a Lee Collet or neck bushing dies your ammo will chamber up a little tight depending how hard you drive it. If you run it hard Remington 700's are already marginal for this case and will flex a little while firing. Your brass is expanding to fill up this slight stretch. You just need full partial full length size enough to bump your shoulders back just enough to facilitate closing the bolt easy. If your full length die will not go down far enough you can either get a custom shell holder or put your die in lathe and cut a couple thousanths off the base of it. The last thing I would do is try to stick a reamer in your chamber and try to pull a single thousanths out of it. Unless you have the same exact reamer the chamber was cut with I doubt it will clean up right. To do it right you need to at least set it back one turn and set your headspace based on a go gauge to freshen up this chamber.

Active Member

Factory stock barrel. Remington 700. First year of 300 RUM manufacture. 1999-2000. Fired brass rechambers fine. no signs of stretching due to firing. Dies are Hornady Custom grade. I checked to see where factory brass was tight and with a totally cold barrel & receiver the factory ammo chambers fine, no effort. With rifle warm from 5 shots over a 5 minute period the factory rounds are difficult to close the bolt on. To me it shows indications of of a chamber with the most minimal dimensions. When I resize the fired brass which easily chambered after being shot it becomes difficult to chamber no matter how I set the dies and I have stated with it barely sizing the neck to down tight on the shellholder and bumping the shoulder back. I would have no problem with just a neck resize. I would like to try a different full length die and try to locate a neck only die. Anyone have a RCBS or LEE 300 RUM die I could size a couple of brass with ?????

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